Poor air flow

Discussion in 'HVAC Heating & Cooling' started by ajbell, Jul 10, 2020.

  1. ajbell

    ajbell New Member

    Jun 8, 2020
    North Carolina
    Hi All
    I am trying to get my AC system to survive one more summer.
    I had to replace the condenser capacitor and the condenser cooling fan motor and
    that seems to be working OK now BUT my system is struggling to cool the house - especially downstairs.

    I have 2 furnace/cooling units in the attic one for downstairs and one for the upstairs.
    (I replaced the condenser capacitor and fan motor for the downstairs unit today)

    The upstairs unit seems to work fine and I can can feel and hear the cool air coming through the vents in the ceiling BUT downstairs I have to stand on a chair with my hand a few inches from the vent to actually feel any air flow. The air is flowing and feels cool but the flow is much less than upstairs.

    When I go into the attic I can hear than the air blower in both the upstairs and downstairs systems is running
    BUT here are the differences:

    1. I can feel cool air coming out of the plastic condensation pipe at the P trap in the upstairs unit
    I can't feel any air flow from the same pipe in the downstairs unit
    (I am sure it was blowing air out of BOTH pipes a couple of weeks ago)
    I attached an image showing this pipe where I can feel the air flow - I don't even know if air is meant
    to be blowing out here??? Is this normal?

    2. The downstairs system is dripping water into the tray - I am sure it was not doing this a couple of weeks ago.

    I don't know much about AC systems so I am just trying to compare the differences in the upstairs and downstairs to help me understand what may be going on.

    Attached Files:

  2. fitter30

    fitter30 Well-Known Member

    Feb 2, 2020
    Retired service tech
    Peace valley missouri
    Condensation should be coming out of the drain hoses on both units. Temperature difference between the supply and return temp 18*-24*. Below 18* unit is either short of refrigerant or compressor not working properly. Obove 24* not moving enough air dkrtybllwer, coil or filter. At the condenser bigger line should be cold if not there is a problem. Furnace lower wheel if the is dirt built up on the cups of the wheel the blower is dirty and maybe the evap coil could be dirty also.
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  4. Sylvan

    Sylvan Still learning

    Sep 23, 2004
    plumbing - fire suppression - boiler inspector
    New York
    Check the filters and the condencer coil for dirt

    Ideally if your using R -22 (older systems) the discharge temperature is around 40 deg F

    When I was a stationary engineer most of the time no one ever pressure washed coils on the hot and cold deck of air handlers

    The roof units had lot of debris blocking the coils especially on a roof located near a resturants exhaused with grease

    The cooling towers had dead birds
  5. WorthFlorida

    WorthFlorida The wife is still training me.

    Oct 28, 2009
    Orlando, Florida
    If you barely feel the air blowing, the fan motor maybe bad. Replacing the caps will not fix a bad motor. The pipe were you feel air is maybe there to flush the condensation line. I can't tell but the coil looks like it is right at the top part of the furnace. I have a feeling the coil or filter is completely blocking airflow and some of it is being pushed out of that pipe which probably sits at the bottom of the drain pan. It could be an overflow. I also don't see a Safe-T-Switch and water stains on the particle board. Past problems I'm sure and be sure to place a cap over the pipe.

    When you think you are getting the proper airflow, and it is still not cooling as it has may be time to have a tech out to put gauges on it.

    Recommendations when you're ready to replace the unit. I highly recommend to go with a heat pump and use the gas furnace as the AUX heat source. If you are to replace the furnace, have it installed suspending from the rafters and a drip pan installed under the AC coil area as an overflow. It will take some duct work. Hanging from the rafter you'll barely hear it running. Right now the floor is acting like a drum.

    I know times can be tough but putting more money into this beast may be not worth it. Like putting money into an old car. You get it fixed then something else goes.
    Last edited: Jul 15, 2020
    Sylvan likes this.
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